2) Also, can I perform a linear regression test on data that is left skewed.

3) I ran a linear regression test on data that was normal and all seemed to go well, testing signf. However, the residual plots do not have a flat line about the line y=0). I see a pattern. Does that say my linear equation doesn't predict? Can I still go with my results from my coef. of det value r^2 and other results from my SPSS output when I did the linear regression test? I am not sure how to interpret the non flat pattern result.

Thanks for your help